Energy giant Royal Dutch/Shell on Tuesday announced a long-term deal with Libya to explore for gas in the energy-rich north African country. The deal, which could see Shell invest as much as $637 million, followed an agreement with the Libyan government 13 months ago to establish a long-term strategic partnership following the former pariah state's return from international wilderness. "The National Oil Corporation of the Great Socialist People's Libyan Arab Jamahiriya (NOC) and Shell Exploration and Production Libya have reached a long-term agreement for a major gas exploration and development deal," a statement issued by Shell said.